Summary http4k is a Kotlin toolkit for building HTTP applications functionally and consistently. It simplifies serving, consuming, and testing HTTP services, targeting developers seeking a lightweight, testable framework for microservices, APIs, and serverless functions. The platform offers modularity and GraalVM compilation for efficient deployment.

How It Works Applications are pure Kotlin functions (HttpHandler), promoting a declarative, testable style. The platform includes a lightweight http4k-core library with JDK-based HTTP implementations, extended by add-on modules. This modular design allows flexible deployment across servers, serverless platforms, or as GraalVM native images, emphasizing simplicity and uniformity.

Quick Start & Requirements Installation involves adding the http4k Bill of Materials (BOM) and desired modules to Kotlin build scripts.

dependencies {
    implementation(platform("org.http4k:http4k-bom: ")) // Use the latest version
    implementation("org.http4k:http4k-core")
    // Add other modules as needed
}

Prerequisites include Kotlin and a JVM; GraalVM compilation is supported for optimized native images. Further details are on the http4k website.

Highlighted Details

• http4k-connect: Client toolkit for third-party cloud/AI services, with fake implementations for testing.
• http4k-ai: Universal LLM adapters (OpenAI, Anthropic, Gemini, Azure, GitHub), LangChain4J integration, agent framework, and in-memory testing.
• http4k-pro: Premium, commercially licensed modules for enterprise needs: Wiretap (OpenTelemetry), X402/MPP payments, Verify (supply-chain security), Hot Reload.
• http4k Enterprise: Offers long-term stability (up to 24-month LTS), enhanced security (SLSA, SBOMs, cosign), priority support, and license reporting for mission-critical apps.

Maintenance & Community The project acknowledges contributions from numerous individuals and companies. Community and detailed project information are available on the official http4k website.

Licensing & Compatibility http4k-pro modules are premium and commercially licensed. The license for http4k-core and other open-source modules is not specified in the provided text. http4k Enterprise features are tailored for regulated, mission-critical environments.

Limitations & Caveats http4k-pro and http4k Enterprise indicate that advanced features, long-term support, and enhanced security assurances are part of commercial packages, not the default open-source distribution. Users requiring these enterprise-grade features must engage with commercial licensing.